Coin operated vending machines commonly include a coin acceptor, a plurality of manually operated selection switches, and a computer or logic board which responds to the operation of one of the selection switches to operate a dispensing mechanism which causes a selected item to move to a position from which the user may remove it from the machine.
Each such dispensing mechanism may include a gear motor which includes a reduction gear train which is driven by the shaft of an electric motor. The motor may be powered through one or more associated switches which are controlled either by the associated computer or by the output shaft of the reduction gear train to stop the operation of the motor when the output shaft of the gear reduction assembly has returned to its initial position.
Vending machines are frequently used in humid and dirty environments which interfere with the operation of the internal mechanisms of the machine such, for example, as the switches which control the operation of the dispensing motors.